1. Field of the Invention
The present invention relates a device and method for controlling integrated circuit (IC) temperature. More precisely, the present invention relates to a device and method for controlling IC temperature applicable to heating or cooling the IC and detecting the temperature thereof during IC performance test.
2. Description of the Related Art
Specifically, the miniscule IC inside the portable electronic device has a low wattage, i.e. approximately less than 2 W or even approximately 1 mW, thereby generating very little heat. So in certain countries with polar climate, the temperature of such an IC tends to drop due to the extremely cold surroundings. As intelligent vehicles start gaining traction, the ICs for these vehicles have to be able to withstand these harsh environments without malfunctioning. Therefore during the manufacturing process for ICs, the ICs of various sizes have to be tested to ensure operation thereof is not compromised under extreme temperature conditions, e.g. industrial grade temperatures (−40° C. to 120° C.) and automotive grade temperatures (above 175° C.).
Usually, the ICs will go through tests such as the Final Test and Reliability Test after packaging. The Final Test consists of heating and cooling the IC. In particular, the IC temperature is lowered to a predetermined value to test whether the IC is able to operate properly under extremely low temperatures, and then the IC temperature is raised to a predetermined value to test whether the IC is able to operate properly under extremely high temperatures. The duration of the Final Test is generally shorter than that of the Reliability Test. In the Reliability Test, the IC is maintained at a high or low temperature and operates continuously while being tested, so as to characterize the operational stability of the IC. During the Reliability Test, the tested IC is baked or cooled for an extended period of time, and all the while the IC is operating, for example for 2 to 3 weeks under a constant predetermined temperature while being tested.
The existing method for testing ICs involves placing the IC in the socket on the printed circuit board (PCB) and then heating up or cooling down the IC while performing tests thereto. A cooling agent may be applied to cool down the IC. The cooling agent cools the socket and the PCB while the IC is tested concurrently. However, since the cooling agent does not come into contact with the tested IC directly, it is difficult for the cooling agent to quickly lower the IC's core temperature despite it being able to lower its overall temperature. On top of that, such a cooling method cannot maintain the tested IC at a constant temperature. To heat the IC up, the tested IC is manually disposed on a hot plate such that the IC is heated to a predetermined temperature. Then the IC is manually moved to and mounted onto the socket, and its performance is tested. However, since the hot plate is no longer able to supply heat to the IC once it has left the hot plate, the IC's temperature drops due to thermal convection in the air while the IC is being moved from the hot plate to the socket and thermal conduction to the socket while the IC is in contact with the socket. Thus, such a heating method fails to maintain the tested IC at a constant temperature. It follows that the test results are inconsistent, since the IC is not tested under the intended constant temperature.
An alternative method for heating up the IC is using a heat gun. However, the use of a heat gun comes with a few caveats which are as follows. (1) Since the heat gun only heats up a specific area with hot air, the IC might not be heated up evenly. The temperature of the hot air cannot be precisely controlled, so the temperature of the hot air might be too high or insufficient. Also, even though the tested IC is thermally insulated by the thermal insulating structure, the hot air of the heat gun might still affect the temperature of the components around the tested IC. (2) Then, when the IC has reached the desired temperature, the heat gun is turned off. The IC then starts to slowly cool and no longer maintains the desired temperature during testing. (3) When the heat gun is heating the tested IC, the components around the IC and the PCB might be heated as well, so the test results might be inaccurate. (4) In order to test a small IC, the tested IC is disposed in the test socket and covered by a lid to ensure electrical contact. This test socket and lid stand in the way of the hot air from the heat gun, thereby making it difficult to heat up the small IC. (5) There is no way to determine the temperature of the IC during testing, let alone the required heating duration.
Another method for heating or cooling ICs involves the thermal stream system. This system is pricey and bulky, consumes a lot of power, and requires compressed gas or air from a compressor to operate. Furthermore, since the tested IC is disposed in the test socket and is of a small size, it might be difficult to heat up or cool down such an IC by applying a stream of hot or cold air. Moreover, the temperature sensor of the thermal stream system is usually disposed at a position where the thermal stream passes, so the temperature sensor will not accurately reflect the temperature of the tested IC. Besides, while it is possible to connect an IC thermocouple to the thermal stream system in order to obtain the IC's temperature, such a thermocouple is usually not disposed in the IC in the testing phase. So, in order to measure the temperature of the tested IC, the thermal stream system has to be connected to such a temperature sensor, which is in turn in contact with or attached to the tested IC to measure the temperature thereof.
The above mentioned method for heating or cooling the IC is extremely inconvenient and is also incapable of obtaining an accurate temperature reading of the IC. The thermal stream system heats up, cools down or maintains the IC at a constant temperature using air flow. However, the operation of thermal stream system on smaller ICs may be hindered due to the socket blocking the flow of air. Also, in particular, there is the need to wait and the extra use of electricity due to the time it takes, usually above 30 minutes, for the thermal stream system to heat up or cool down the IC. And even though a plurality of temperature sensors can be applied to measure the individual temperatures of a plurality of ICs, the configurations of the temperature sensors have to be readjusted for further testing of the ICs. Hence, such a solution is not convenient to use and renders the IC test inefficient. On top of that, during the heating or cooling of the tested IC, the components around the IC might also be heated or cooled. So, the thermal stream system is not capable of solely heating up or cooling down the IC, which leads to the likely deviation from optimum working temperatures of the surrounding components. Therefore, the results for the IC test are significantly affected. In addition, because the surrounding components tend to deviate from optimum working temperatures, locating any faulty ICs will be a challenging task when testing a plurality of ICs. This is thus an inconvenient method for temperature testing of ICs.